diff --git a/src/runestone.jl b/src/runestone.jl
index 5914417..47cd2ae 100644
--- a/src/runestone.jl
+++ b/src/runestone.jl
@@ -1074,12 +1074,16 @@ function replace_with_in_filter(ctx::Context, node::Node)
     @assert kind(node) === K"filter" && !is_leaf(node)
     pos = position(ctx.fmt_io)
     kids = verified_kids(node)
-    idx = findfirst(x -> kind(x) === K"=" && !is_leaf(x), kids)::Int
+    idx = findfirst(x -> kind(x) in KSet"= cartesian_iterator" && !is_leaf(x), kids)::Int
     for i in 1:(idx - 1)
         accept_node!(ctx, kids[i])
     end
     kid = kids[idx]
-    kid′ = replace_with_in(ctx, kid)
+    if kind(kid) === K"="
+        kid′ = replace_with_in(ctx, kid)
+    else
+        kid′ = replace_with_in_cartesian(ctx, kid)
+    end
     if kid′ === nothing
         seek(ctx.fmt_io, pos)
         return nothing
diff --git a/test/runtests.jl b/test/runtests.jl
index ac8453c..5739ade 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -434,6 +434,8 @@ end
         for (l, r) in (("[", "]"), ("(", ")"))
             @test format_string("$(l)i for i$(sp)$(op)$(sp)I if i < 2$(r)") ==
                 "$(l)i for i in I if i < 2$(r)"
+            @test format_string("$(l)i for i$(sp)$(op)$(sp)I, j$(sp)$(op)$(sp)J if i < j$(r)") ==
+                "$(l)i for i in I, j in J if i < j$(r)"
         end
     end
 end